Python-Daemon - Library to implement a well-behaved Unix daemon process. | Hacker News Reader

Python-Daemon - Library to implement a well-behaved Unix daemon process.

pypi.python.org

63 pointsrams10 comments

I tend to think this is the wrong way to go about daemonizing a process; it does the relatively easy but fiddly stuff for you, leaving you still to manage process monitoring.

Better to have the process neither know not care about its daemonized status, which is not really core program logic, and have the process monitor manage daemonization, à la http://cr.yp.to/daemontools.html

Twisted Python comes with its own "twistd" script to daemonize a Twisted application. Sure, not every Python daemon is written in Twisted, but most daemons talk to a TCP, UDP, or Unix socket for something, which means Twisted is a tool you're likely to be evaluating anyway.

I haven't tried this, but it sure looks handy. Writing a daemon is a common task, but not so often (for me, anyway) that it feels like copy-and-pasting the same boilerplate every time. So, I ignore the old rule that says "if you're going to do it more than once, write a program to do it for you". I always end up writing a one-off prototype for my own personal use, and then upgrading it to be a daemon, and I make the same Google searches every time. I'll have to try this next time.

writing a daemon is not necessarily a repetitive process, all the stuff that you "have to do" are driven by engineering demands. You have to think of them consciously before you do each one and there is no particular number of them and no particular order, it's all dictated by your application: when to fork and let the parent die? when to give up terminal? change directory? reset/change umask? what file descriptors to close which ones to open and what to keep? logging? other IPC channels for client apps? etc.

this stuff is not cruft or boiler-plate is it? also, you shouldn't be writing daemons so often as to need a framework, and if you do, you better understand all that goes into it.

I agree that it's not boiler-plate, and I don't mean that I do it all that often, maybe every six months or so when I find something new I want my home server to do. (Like the last one, experimenting with port knocking) I am by no means a professional programmer, that's why I find myself making the same searches.

Cheers! didn't mean to come off so nanny-like ;-)

I'd like to learn more about daemons to satisfy my own personal curiosity. Do you have any resources you recommend?

Richard Stevens's "Advanced Programming in the UNIX Environment" has a chapter dedicated to how to write well-behaved daemons. The book is a great investment if you are doing any kind of UNIX programming; I highly recommend it.

This one is the one I use for several applications http://www.jejik.com/articles/2007/02/a_simple_unix_linux_da...

if you're using ruby, check out daemons and especially daemon-kit which includes a nice rapleaf patch to daemons

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